Popcorn is made from un-popped corn kernels by heating the kernels until they “pop.” Popcorn kernels have a hard, outer hull that is generally impervious to moisture, while inside the hull the kernel contains starch and proteins with a certain amount of moisture and oil. Heating the kernels turns the moisture inside the hull into a superheated pressurized steam, which causes the starch to gelatinize and pressure to build up in the kernel until the hull ruptures. When the hull ruptures, the pressure quickly drops, allowing the steam to expand. The expanding steam causes the gelatinized starch and proteins inside the kernel to expand into an airy foam, which when cooled sets into the typical popcorn “flake” or “puff.”
Early methods for making popcorn involved heating kernels in a basket over an open fire or flame, producing hot, dry, unevenly cooked popcorn. Other methods used oils and fats to aid in heating the kernels, such as in pan frying and frying machines, such as those developed by Charles Cretors in 1885. Later-developed appliances use hot air to heat the kernels and blow the popped kernels out a chute. More recently, standard microwave appliances are used to heat popcorn kernels in a bag containing the kernels and grease or fat.
The above methods have various disadvantages. One common disadvantage to all, however, is that they take too much time to produce suitable quantities of popcorn on demand which results in limited availability, and require advance preparation of large quantities of popcorn which results in product that may not remain fresh. The methods used previously also result in non-uniform heating of the popcorn kernels, resulting in uneven or incomplete popping or kernels and a portion of the hard shell of many kernels remaining un-popped. Although standard multi-mode kitchen microwave devices have been used in the art for popping popcorn, the long processing times also often result in burning of a significant number of popcorn kernels and popcorn flakes, which also affects the taste and aroma characteristics of popped flakes in the same container as the burned kernels and burned flakes. The above considerations add to the processing time, costs of production, loss in efficiency, and quality of end product.
Yet another disadvantage of most method of making popcorn is that a relatively large percentage of the kernels never pop. This results in decreased yield and often results in a person occasionally biting down on an un-popped kernel. Moreover, many consumers of popcorn inadvertently heat popcorn kernels too long, which result in burned popped flakes having toxic levels of heterocyclic amines (HCAs) and polycyclic aromatice hydrocarbons (PAHs) that are potentially carcinogenic. For example, the Ohmy News International Science and Technology website recently published a list of the top 10 carcinogenic foods, with burned popcorn at the top of the list (http://english.ohmynews.com/articleview/article_view.asp?at_code=436169). In addition, recent reports suggest that chemicals present in many microwave popcorn products (to impart flavorings, such as butter flavor), as well as chemicals released from the packaging of microwave popcorn bag itself, are also potentially toxic and carcinogenic.
Improvements in the prior art methods have been subject to certain constraints. The prior art specifically teaches that popping results are sensitive to the rate at which the kernels are heated. For example, the Wikipedia webpage for “Popcorn” teaches that if heated too quickly, the steam in the outer layers of the kernel can reach high pressures and rupture the hull before the starch in the center of the kernel can fully gelatinize, leading to partially popped kernels with hard centers, and, if heated too slowly, leads to entirely un-popped kernels. Because a kernel is not entirely moisture-proof, moisture can leak out of the tip when it is heated slowly, keeping the pressure from rising sufficiently to break the hull and cause the kernel to pop.
The various aspects and embodiments of the present invention, as described below, represent novel improvements on the above devices and methods of the prior art. In addition, the methods and devices of the present invention produce novel popcorn flakes having unexpected and surprisingly lower density and higher popping efficiency (more complete popping with less residual shell remaining).